Final answer:
The correct retractor used during a median sternotomy is the Finochietto retractor. It is specifically designed for thoracic surgery and provides access to the heart and lungs.
Step-by-step explanation:
During a median sternotomy, the most commonly used retractor is the Finochietto retractor. This retractor is specifically designed for thoracic surgery and is utilized to separate the edges of the sternum, providing access to the heart and lungs. The Balfour retractor is typically used in abdominal surgery, the Army-Navy retractor is used for smaller incisions in a variety of surgeries, and the Gelpi retractor is used in orthopedic and neurosurgery.
Therefore, the correct answer to which retractor is used in a median sternotomy is A. Finochietto retractor. This piece of surgical equipment is named after the Argentine surgeon Enrique Finochietto, who is credited with its invention. It is considered an essential tool in cardiothoracic surgery.